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Sudan Journal of Agricultural Research
Transformation of urea in the soil of Kenana Scheme
A.I. Adam1, O.A. Ali 2, A.A. Salih 3. and M. Brouwers4
Abstract:
Transformation of urea was monitored in a high yielding field (field 32119) and a low yielding field (field 22101) on the same soil in Kenana Sugar Company. Ensuing urea application, wet soil samples were obtained from ridge positions by an auger from 0-15, 30-45, 60-75, and 90-105 cm on day 0, 7,15,30,60,90,120,150 and 180 from application. NH4+__ N and NO3-__ N were extracted by 1N KCI and measured by an automatic analyser. Results showed that NH4+__ N and NO3-__ N in the 0-15 cm depth prior to urea application were low and that NO3-__ N was not detected at lower depths in the two fields. In field 32119, the NH4+__ N in the top 15 cm reached 35.55 mg N kg -1. soil at 60 days and henceforth sharply decreased with time, whereas the NO3-__ N increased to 12.45 mg N kg -1 soil at 60 days and then gradually decreased. In case of field 22101, the NH4+__ Nin the top 15 cm reached 34.10 mg N kg -1 soil at day 15 then gradually decreased with time. Whereas the NO3-__ N reached 36.55 mg N kg -1 soil at day 7, then decreased with time. Depthwise both NH4+__ N and NO3-__ N were markedly reduced below 30 cm in both fields. The study revealed that mineral N is mainly concentrated in the top 15 cm layer for about 4 months ensuing urea application and to a lesser extent in the 30-45 cm layer whereas at lower depths the amount of mineral N is very low.
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Sudan Journal of Agricultural Research Vol. 3(2000) PP. 15-19
